We are turning up a DMVPN tunnel network that will have 400+ spokes on it. Curious to know if there are any recommendations on maximum subnet size that should be used on the tunnel. Can I get away with creating a /23 or a /22? Since DMVPN is NBMA, I would think that it doesn't suffer from all the broadcast traffic you would get on an Ethernet network so going bigger than a /24 might be OK. We would be running OSPF on the DMVPN tunnel to peer with the spokes. I don't believe the old rule of no more than 50 devices in an area applies anymore so I'm less worried about OSPF.
Thoughts?
